In the functional processes alluded to in the preceding chapter, the
male germ-cell and the female germ-cell unite in a practically equal
division of substance. We say "practically" because the maternal and
the paternal influences are not equally divided in the offspring. One
or the other usually predominates. But, as a general rule, it may be
said that in the development of the embryonal life the process of cell
division proceeds in such a way that every germ of the child's future
organism represents approximately one-half maternal and one-half
paternal substance and energy.
In this process lies the true secret of heredity. The inherited
energies retain their full measure of power, and all their original
quality in the growing and dividing chromosomes (the chromosome is one
of the segments into which the chromoplasmic filaments of a
cell-nucleus break up just before indirect division). On the other
hand, the egg-substance of the female germ-cell, which is assimilated
by the chromosomes, and which is turned into _their_ substance by the
process of organic chemistry, loses its specific plastic vital energy
completely. It is in the same way that food eaten by the adult has
absolutely no effect on his qualitative organic structure. We may eat
ever so many beef-steaks without acquiring any of the characteristics
of an ox. And the germ-cell may devour any amount of egg-protoplasma
without losing its original paternal energy. As a rule a child
inherits as many qualities from its mother as from its father.
DETERMINATION OF SEX
Sex is determined after conception has taken place. At an early stage
of the embryo certain cells are set apart. These, later, form the sex
glands. Modern research claims to have discovered the secret of
absolutely determining sex in the human embryo, but even if these
claims are valid they have not as yet met with any general
application.
EARLY DEVELOPMENT
Some twelve days after conception, the female ovule or egg, which has
been impregnated by the male spermatazooen, escapes from the ovary
where it was impregnated, and entering a tube (Fallopian) gradually
descends by means of it into the cavity of the womb or uterus. Here
the little germ begins to mature in order to develop into an exact
counterpart of its parents. In the human being the womb has only a